Thin-film Composite Polyamide Nanofiltration Membrane Research Articles

Antimicrobial thin-film composite polyamide nanofiltration membrane with high desalination and flux performance manufactured through a novel UV light driven photoreduction method that generates dispersed silver nanoparticles

Antimicrobial thin-film composite polyamide nanofiltration membrane with high desalination and flux performance manufactured through a novel UV light driven photoreduction method that generates dispersed silver nanoparticles

Fabrication of thin-film composite polyamide nanofiltration membrane based on polyphenol intermediate layer with enhanced desalination performance

Nanofiltration (NF) membrane is of great significance for desalination of light brine and purification of drinking water. Although the development of novel preparation methods and membrane materials has improved the separation performance, it is still a major challenge to promote NF membrane toward industrial production with simpler and more controllable process. Herein, the polyphenol intermediate layer was designed by 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI) with twist structure and polyethyleneimine (PEI) co-deposition to increase the surface hydrophilicity and electropositivity of the polysulfone ultrafiltration substrate. Subsequently interfacial polymerization (IP) was carried out on the polyphenol intermediate layer to assemble a polyamide ultrathin selective layer using trimesoyl chloride and piperazine monomer. Through adjusting the co-deposition time of TTSB and PEI, a unique nano-pleated structure was successfully formed on the thin-film composite membrane surface. The water permeance of the membrane was determined as 23.7 L m−2 h−1 bar−1 with 99.4% Na2SO4 rejection, which was almost triple fold of the flux of the controller membrane without the intermediate layer. Our results provide an efficient and convenient way to fabricate the advanced NF membrane with higher divalent/monovalent ion selectivity and water permeance simultaneously, which will provide advices for the gas separation and pervaporation membranes with the IP method.

Improving the water permeability and antifouling property of thin-film composite polyamide nanofiltration membrane by modifying the active layer with triethanolamine

Interfacially synthesized polyamide (PA) thin-film composite (TFC) membranes, as the state-of-the-art polymeric membranes for nanofiltration (NF), are prone to fouling in processing wastewaters and industrial fluids due to the inherent surface physicochemical properties of polyamide active layer. Here, we report the facile and effective modification of PA-TFC nanofiltration membranes for improved water permeability and antifouling property by surface grafting. Ttriethanolamine (TEOA) molecules were bonded onto the surface of PA-TFC NF membrane through esterification reaction between the hydroxyl groups of TEOA and the residual acyl chloride groups on the nascent PA-TFC membrane by pouring the TEOA aqueous solution on membrane surface. The covalent attachment of TEOA molecules was shown to tailor the surface chemistry of the composite membrane without altering the morphology of active layer. The PA-TFC membrane became more hydrophilic after modification and thus more permeable to water and antifouling against hydrophobic foulants, while maintaining its molecular weight cut-off. The results of tertiary treatment of industrial effluent also demonstrated that the modification performed in our study could effectively improve the water permeability and antifouling property of the PA-TFC NF membrane in processing wastewater.

Submerged nanofiltration of biologically treated molasses fermentation wastewater for the removal of melanoidins

The possibility and efficiency of submerged nanofiltration (SNF) in the removal of melanoidins from the biologically treated molasses fermentation wastewater were evaluated in this study. Submerged filtration tests were conducted with biologically treated molasses fermentation effluent employing lab-made membrane modules manufactured from lab-fabricated flat-sheet thin-film composite polyamide nanofiltration membranes with a molecular weight cut-off (MWCO) of about 580Da. Treatment efficiency in terms of color removal, permeate flux as well as COD reduction was investigated under different trans-membrane pressures (TMPs) and various volume concentrating factors (VCFs). The results showed that melanoidins could be effectively removed from the biologically treated molasses fermentation wastewater by submerged nanofiltration and the electrolytes presented in the effluent were nearly not retained by the membrane, so that the nanofiltration membrane module could be operated under a low suction pressure. Both the removal efficiency of melanoidins and the reduction ratio of COD increased with the increase of TMP and/or VCF at the expense of water permeability. Steady flux of 3.90L/m2h, color removal ratio of 99.5% and COD reduction ratio of 93.8% could be achieved by the submerged nanofiltration system operated under the TMP of 0.8bar and VCF of 4.0. Furthermore, under the same VCF, compared with the pressurized nanofiltration system (PNF), the SNF system is more anti-fouling and easily to be physically cleaned.

Study on polyamide thin-film composite nanofiltration membrane by interfacial polymerization of polyvinylamine (PVAm) and isophthaloyl chloride (IPC)

A novel thin-film composite polyamide nanofiltration membrane was prepared through interfacial polymerization of polymeric polyamine polyvinylamine (PVAm) with isophthaloyl chloride (IPC) on a polysulfone supporting film. The composite membranes were prepared under different conditions and characterized in terms of chemical and morphological structures, surface zeta potential, pure water permeability, and rejection to different solutes including electrolytes and sucrose. The results showed that the membrane performance was significantly affected by the content of amine units of PVAm and the concentrations of PVAm and IPC. The increase of the content of amine units of PVAm and the concentration of IPC resulted in an augment in salt rejection and a decrease in permeability, while the increase of PVAm concentration led to enhancement in both the salt rejection and water flux. The obtained membranes were positively charged at pHs lower than 6.5 and negatively charged at pHs higher than 7.0. The rejection order of the membrane changed from MgCl 2 > MgSO 4 > NaCl > Na 2SO 4 at pH 3.0 to MgSO 4 > Na 2SO 4 > MgCl 2 > NaCl at pH 7.5. The decrease of feed pH from 7.5 to 3.0 resulted in an over 35.0% augment in permeability. Furthermore, the novel nanofiltration membrane is of good performance stability and particularly suitable for treating acidic feed.

Interlaboratory studies of highly permeable thin‐film composite polyamide nanofiltration membrane

The aim of this paper is to survey interlaboratory studies of performance data to produce highly permeable thin‐film composite (TFC) polyamide nanofiltration (NF) membrane in the form of flat sheet at bench scale. TFC polyamide NF membranes were fabricated via interfacial polymerization of 1,3‐phenylenediamine and trimesoyl chloride on porous polyethersulfone (PES) membrane. The NF membranes were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and cross‐flow filtration. The AFM and SEM analyses indicated that a rough and dense film was formed on the PES support membrane. The permeability and NaCl rejection of the NF membrane prepared at the presence of camphor sulfonic acid as pH regulator and triethylamine as accelerator in the aqueous solution were 21 l m−2 h−1 and 70%, respectively. In order to estimate the repeatability and reproducibility standard deviations, the development of an interlaboratory study was conducted by measurements of permeation flux and salt rejection of the synthesized membranes. Repeatability standard deviation of the permeation flux data for the membrane based on optimum formulation was 1.99, and reproducibility standard deviation was 3.55. Also based on this trend, repeatability standard deviation of the salt rejection data was 1.57, and reproducibility standard deviation was 4.11. The American Society for Testing and Materials standard E691‐05 was used for data validation of the repeatability and reproducibility standard deviations and consistency statistics. Copyright © 2011 John Wiley & Sons, Ltd.

Effect of pH on the performance of polyamide/polyacrylonitrile based thin film composite membranes

In this study the effect of pH on the performance of thin film composite (TFC) nanofiltration (NF) membranes has been investigated at the relevant pH conditions, in the range of pH 1–13. TFC polyamide NF membranes have been fabricated on a polyacrylonitrile support via interfacial polymerization between piperazine in an aqueous phase and trimesoyl chloride in an organic phase. Membrane characterization has revealed that the produced membranes show a NaCl retention similar to NF-270 and Desal-5DK, a permeance in between those of NF-270 and Desal-5DK, and a slightly higher iso-electric point than NF-270 and Desal-5DK. The molecular weight cut-off of the membranes appeared to be practically constant in acidic and neutral conditions. At extremely alkaline conditions (pH > 11) an increase in molecular weight cut-off and a reduction in membrane flux has been observed. According to the Donnan steric partitioning pore model (DSPM) the change in performance in alkaline conditions originates from a larger effective average pore size and a larger effective membrane thickness as compared to the other pH conditions.

Evaluation and characterisation of TFC-PA Nanofiltration membrane for the rejection of cadmium from aqueous solutions

Performance of a thin-film composite polyamide nanofiltration membrane has been studied to separate cadmium ions from aqueous solutions. The operating variables studied are pressure, concentration and feed flowrate. It is observed that the solute rejection increases with increase in applied pressure and decreases with increase in feed concentration at constant feed flowrate. The maximum observed rejection of the metal ion is found to be 82.87 and 64.86% for feed concentration of 5 and 250 ppm, respectively. Cadmium ion rejection is sensitive to pH change. Membrane transport parameters and mass transfer coefficients are estimated using different models.

Preparation and characterization of asymmetric polyethersulfone and thin-film composite polyamide nanofiltration membranes for water softening

In this research, two types of nanofiltration membranes were prepared and evaluated for water softening. Their nanofiltration performance was evaluated by cross-flow filtration using NaCl (1 g/l) and MgSO 4 (1 g/l) solution at 5 and 10 bar, 25 °C and 10 l/min. The morphological studies were performed with SEM and AFM instruments. In addition, the hydrophilicity of membranes was examined by contact angle measurements. In the first type, asymmetric polyethersulfone (PES) nanofiltration membranes were prepared using phase inversion induced by immersion precipitation technique. Different components such as polyvinylpyrrolidone (PVP), polyethyleneglycole (PEG), acrylic acid and Triton X-100 were used as additive in the PES casting solution, which lead to the formation of new asymmetric nanofiltration membranes. Two concentrations of PES (20 and 25 wt%) and two different non-solvents (pure water and mixture of water (80 vol.%) and IPA (20 vol.%)) were used for preparing asymmetric nanofiltration membranes. The morphological studies showed that the membranes prepared with non-solvent containing 20 vol.% IPA have smoother surface and smaller pores in surface and sub-layer compared to membranes prepared with pure water as non-solvent. The flux was decreased when higher polymer concentration and mixture of water and IPA were employed for membrane formation. However, NaCl and MgSO 4 rejections were improved. In the second type, thin-film composite polyamide nanofiltration membrane was fabricated using interfacial polymerization of 1,3-phenylenediamine (PDA) with trimesoyl chloride (TMC). A rough and dense film was formed on the PES support membrane by interfacial polymerization. The water permeability of composite membrane was 7 and 21 kg m −2 h −1 at 5 and 10 bar, respectively. Moreover, the rejection to the MgSO 4 as divalent salt (85 and 90%) was high compared to the NaCl as monovalent salt (64 and 67%).

Application of nanofiltration for the rejection of nickel ions from aqueous solutions and estimation of membrane transport parameters

The present work deals with the application of a thin-film composite polyamide nanofiltration membrane for the rejection of nickel ions from aqueous wastewater. The operating variables studied are feed concentration (5–250 ppm), applied pressure (4–20 atm), feed flowrate (5–15 L/min) and pH (2–8). It is observed that the observed rejection of nickel ions increases with increase in feed pressure and decreases with increase in feed concentration at constant feed flowrate. The maximum observed rejection of the metal is found to be 98% and 92% for an initial feed concentration of 5 and 250 ppm, respectively. The effect of pH on the rejection of nickel ions and permeate flux are studied, and found that the variation in pH is having more effect on the latter than the former. The experimental data are analyzed using membrane transport models; combined-film theory-solution-diffusion (CFSD), combined-film theory-Spiegler–Kedem (CFSK) and combined-film theory-finely porous (CFFP) models; to estimate membrane transport parameters and mass transfer coefficient, k. Also, enrichment factor, concentration polarization modulus and Peclet number are found from various parameters. From CFFP model the effective membrane thickness and active skin layer thickness are found.